Image forming apparatus with controller for controlling voltage at transfer nip

Abstract

An image forming apparatus includes an image bearing member, a transfer member, a voltage source, a current detecting portion, and a controller. In a case that the predetermined voltage is changed in a first job on the basis of the detection result of the current detecting portion during passing of the recording material through the transfer portion, in a second job subsequent to the first job, when a first recording material of the second job passes through the transfer portion, the controller changes a voltage applied to the transfer member on the basis of the predetermined voltage changed in the first job.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 an image forming portion configured to form a toner image; 
 an intermediate transfer belt to which the toner image formed by the image forming portion is transferred; 
 an inner roller in contact with the inner surface of the intermediate transfer belt; 
 an outer roller forming a transfer nip for nipping a recording material and for transferring the toner image from the intermediate transfer belt to the recording material in cooperation with the inner roller; 
 a voltage source configured to apply a voltage to one of the inner roller and the outer roller; 
 a current detecting portion configured to detect information on a current flowing through the inner roller or the outer roller; and 
 a controller configured to control the voltage source, 
 wherein the controller is configured to perform constant voltage control so that the voltage applied from the voltage source becomes a target voltage in a case in which the detection result detected by the current detecting portion is within a predetermined range defined by at least one of an upper limit value and a lower limit value based on the type of the recording material while the recording material passes through the transfer nip, and 
 wherein, in a case in which the detection is out of the predetermined range while the recording material passes through the transfer nip, the controller is configured (i) to adjust the target voltage so that the detection result falls within the predetermined range, and (ii) to perform constant voltage control with the adjusted target voltage while the recording material passes through the transfer nip, and 
 wherein, in a case in which the detection result is out of the predetermined range while a first recording material in a first job passes through the transfer nip, the controller is configured (i) to adjust the target voltage while the first recording material in the first job passes through the transfer nip, and (ii) to adjust the target voltage to be applied by the voltage source, while a first recording material in a second job, which follows the first job, passes through the transfer nip, on the basis of the adjusted target voltage adjusted while the first recording material in the first job passes through the transfer nip. 
 
     
     
       2. An image forming apparatus according to  claim 1 , further comprising,
 a feeding portion provided so as to be openable and closable and configured to accommodate and feed the recording material supplied to the transfer nip, and 
 an open/close detecting portion configured to detect opening and closing of the feeding portion, 
 wherein in a case that each of the first recording material in the first job and the first recording material in the second job is fed from the feeding portion and the open/close of the feeding portion is detected by the open/close detecting portion in a period between the first job and the second job, the controller sets, at a preset value, the voltage applied to the transfer belt when the leading end portion of the first recording material in the second job passes through the transfer nip. 
 
     
     
       3. An image forming apparatus according to  claim 1 , further comprising a plurality of feeding portions each provided so as to be openable and closable, each of the plurality of feeding portions being configured to accommodate and feed the recording material supplied to the transfer nip,
 wherein, in a case that the feeding portion used in the first job and the feeding portion used in the second job are different from each other, even when the predetermined voltage is changed during execution of the first job the controller sets, at a preset value, the voltage applied to the transfer belt when the leading end portion of the first recording material in the second job passes through the transfer nip. 
 
     
     
       4. An image forming apparatus according to  claim 1 , further comprising an operating portion configured to set the voltage applied to the transfer belt by an input operation by a user,
 wherein, in a case that the voltage applied to the transfer belt is changed by the operating portion in a period between the first job and the second job, even when the predetermined voltage is changed during execution of the first job the controller sets, at a preset value, the voltage applied to the transfer belt when the leading end portion of the first recording material in the second job passes through the transfer nip. 
 
     
     
       5. An image forming apparatus according to  claim 1 , wherein, in a case that the image forming apparatus goes to a sleep state in a period between the first job and the second job, even when the predetermined voltage is changed during execution of the first job the controller sets, at a preset value, the voltage applied to the transfer belt when the leading end portion of the first recording material in the second job passes through the transfer nip. 
     
     
       6. An image forming apparatus according to  claim 1 , wherein in a case that the second job is started after a lapse of a predetermined time from an end of the first job, even when the predetermined voltage is changed during execution of the first job the controller sets, at a preset value, the voltage applied to the transfer belt when the leading end portion of the first recording material in the second job passes through the transfer nip. 
     
     
       7. An image forming apparatus according to  claim 1 , wherein the controller is configured to execute an operation for outputting a test chart for adjusting the voltage applied to the transfer belt and for adjusting the voltage applied to the transfer belt based on the test chart, and
 wherein, in a case that the operation is executed in a period between the first job and the second job, even when the predetermined voltage is changed during execution of the first job, the controller sets, at a preset value, the voltage applied to the transfer belt when the leading end portion of the first recording material in the second job passes through the transfer nip.